As cellulose material producing bacteria, Acetobacter strains (Acetobacter) such as Acetobacter xylinum subsp. sucrofermentans represented by the BPR2001 strain, Acetobacter xylinum ATCC23768, Acetobacter xylinum ATCC23769, Acetobacter pasteurianus ATCC10245, Acetobacter xylinum ATCC14851, Acetobacter xylinum ATCC11142 and Acetobacter xylinum ATCC10821, Agrobacterium, Rhizobium, Sarcina, Pseudomonas, Achromobacter, Alcaligenes, Aerobacter, Azotobacter, Zeuglare, various kinds of variants produced by variation of those bacteria by the known methods using NTG (nitrosoguanidine) and the like, and so on have been known.
Methods intended for improving the production efficiency of cellulose with Acetobacter strains have been proposed in a great number of patent applications including those filed by Biopolymer Research Co., Ltd. Methods of acquiring mutants and methods of using expensive and special agents are described in, for example, JP-A-62-265990, JP-A-63-202394, JP-A-63-74490, JP-A-2-238888, JP-B-6-43443, JP-B-5-1718, JP-A-7-184677 and JP-A-7-184675. Methods for controlling the conditions of the culture under agitation are disclosed in, for example, JP-A-9-94094 and the like.
In the known culture methods described above, a very small amount of water-soluble polysaccharide is produced at the same time, but almost all the cellulose material as a main product is recognized as a cellulose having β-1,4-glycoside linkages, and the ratio of Iα-crystals to Iβ crystals ((Iα/Iβ)×100, hereinafter referred to as Iα fraction), which is used in cellulose crystallography, is considered to be 64 to 72% (SCIENCE, Vol. 223, 283 (1984)). The Iα crystal essentially has a low surface activity, such as wettability, because when a specific crystal plane, particularly a (11-0) plane, is oriented, the hydroxyl group density in the crystal plane is lower than that of the Iβ crystal. Thus, a cellulose material produced by conventional microorganisms such as Acetobacter strains, in which the Iα fraction is as high as 64 to 72% and the (11-0) plane is oriented, essentially has a low surface activity.
Some patent publications disclose examples in which the cellulose conversion efficiency with respect to sugars that are used as carbon sources is 30% or greater in the production of the cellulose based material in the Acetobacter strains culture method. However, it can be considered that the cellulose conversion efficiency at a practical level is about twenty-odd %. These known culture methods are complicated in terms of their operation because a spinner culture acquires special features in view of the fact that Acetobacter strains which are aerobic bacteria are used.
Generally, spinner culture is used as an industrial production method, and the basic morphology of a produced cellulose material is disclosed in U.S. Pat. No. 5,144,021 (1992). According to the US patent, the cellulose material has a spherical or ellipsoidal shape with the size of about 0.1 to 10 mm as a macroscopic structure, the internal structure thereof is an interconnected network, and it is thus considered that the cellulose material has characteristics such that resistance to compression when wetted is high. However, high resistance to compression also means that it is hard for water to drain and thus drying is difficult. Furthermore, since fibrils extending radially do not exist around the above spherical or elliptic macroscopic structure, it can be considered that considerable energy is required for mutually and uniformly dispersing the macroscopic structures. Furthermore, according to U.S. Pat. No. 5,144,021, the degree of crystallinity is not so high, i.e. 70% or less, and it is thus conceivable that the strength of the cellulose itself and the performance when combined with other polymer material are poor.
A loosened material of bacteria cellulose having a sedimentation compression degree of 0.12 to 0.20 is disclosed in JP-B-2,877,676. Bacteria cellulose characterized in that the dynamic viscosity of an aqueous suspension of 0.1% bacteria cellulose is 1000 cp or greater (30° C., 10 rad/s) is disclosed in JP-B-2,971,024. These disclosures, like that of JP-B-6-43443, indicate that bacteria cellulose easily entraps water, and the conventional cellulose material has high thickening and dispersion effects, but has a disadvantage that considerable energy is consumed for processing the material into a solid product. On the other hand, bacterial cellulose produced by Acetobacter strains is used commercially only as acoustic oscillation plates.
Development of bacteria cellulose as food additives has been examined but has not resulted in actual commercialization. This is considered to be partly attributed to the fact that although the fibril produced by Acetobacter strains has remarkable characteristics of being as thin as several nm in diameter, its macroscopic morphology is simply an ellipsoid and is far from advantageous for processing as compared with other fibrous materials. Furthermore, as another reason, it is also considered to be attributed to the fact that bacterial cellulose has not been produced in a culture in a really functional manner.
The present inventors found through gene analysis of 16S-rRNA that microorganisms (CJF002 strain) highly homologous with Enterobacter produced a cellulose-like material, and filed a patent application for an invention of a method of applying the microorganisms to the tertiary recovery of petroleum (JP-A-2001-321164). In the patent application, static culture is described as a preferred culture method, and a method for blocking a water sweeping channel of a petroleum bedrock by the products of the microorganisms is disclosed, but the detailed structure, function and the like of various kinds of carbon sources relating to the produced cellulose-like material are not disclosed.